Adjustable pipe joint

ABSTRACT

The present invention discloses a universal, adjustable pipe joint which permits a wide variety of possible adjustments with simple means in well drilling technology. In principle, the joint disclosed in this invention can be readily used for joining articles of all types which included tubular, pipe-like, projections.

This is a continuation-in-part of patent application Ser. No. 07/608,292filed on Nov. 1, 1991, now issued as U.S. Pat. No. 5,101,915.

BACKGROUND OF THE INVENTION

The present invention discloses a novel adjustable tool joint of twopipe sections that form part of a drill string casing, for example, adeep drilling tool casing for a directional drilling motor.

A known pipe joint of this type, as disclosed in U.S. Pat. No.4,813,497, serves to impart a neutral axial alignment to the pipesections that are to be joined and this alignment can be varied within agiven bending angle range. This pipe joint consists of a total of fivecomponents and includes a tubular inside part that can be screwed in atone end and which also has an outside thread coinciding with the insidethread of one of the pipe sections to which it is to be joined. Theoutside thread of this inside part has a thread axis which forms anangle with the main axis of the inside equal to half the size of themaximum possible bending angle for the pipe joint.

A tubular connecting part is provided on the inside part so that theconnecting part can move axially over and rotate above the main axis ofthe inside part. This tubular connecting part has an outside thread onone end that can be screwed with the inside thread of the other pipesection to be joined. This outside thread has a thread axis which alsoforms an acute angle with the main axis of the inside part and whichcorresponds to half the size of the maximum possible bend angle of thepipe joint. The connecting part also has facing teeth on the end facingaway from its outside threads, and by means of these teeth it engageswith the facing teeth on a tubular outside part which can move axiallyover the inside part but which is prevented from turning about the mainaxis of the inside part.

The outside part and the connecting part are held in mutual engagementby two nuts, each of which sits with its outside thread on the insidepart in a screwed engagement, and the parts are held in compressiveengagement on their facing ends with the other ends of the outside partand the connecting part facing away from each other. Be releasing thecompressive engagement between the outside part and the nut engaged withit, the outside part can be moved with the connecting part and theconnecting part can be turned to the desired extent relative to andabout the main axis of the inside part. The locking engagement betweenthe outside part and the connecting part can be restored and secured btightening the nut acting on the outside part.

Depending on the alignment of the connecting part relative to the insidepart, a bend angle can be adjusted between the axes of the pipe sectionsto be connected with this pipe joint. This bend angle has a range whoseminimum value is zero and whose maximum value is based on the sum of theangles about which the hinge axes of the connecting thread for the pipesections to be joined are bent from the main axis of the inside part ofthe pipe joint.

Such a pipe joint is complicated in its design and handling, has areduced strength in comparison with the strength of the joined pipesections, permits angle changes only in the stages determined by thefacing teeth between the outside part and the connecting part, and doesnot present a closed exterior contour in the area of the joint.

In another known pipe joint design including an adjustable angle of bendbetween the pipe sections to be joined, as disclosed in U.S. Pat. No.4,8I7,740, two pipe bodies which are part of the pipe joint areconnected directly to each other by way of threads whose axes are bentat an angle. The bend angle between the pipe sections of the drillcasing to be joined changes with the length of engagement of the angledthreads of the two bodies that are to be screwed together. Theengagement length is determined by spacers placed between the two pipebodies.

Such a design is also complicated structurally and in its fieldhandling, permits only stepwise adjustments in the bend angle betweenthe pipe sections to be joined as a function of the gradation in theavailable spacers, and causes an adjustment in the axial distancebetween the pipe sections to be joined when the angle of the bend isadjusted.

There is also a known pipe joint where the pipe sections of a drillcasing are joined together with a screw connection, as disclosed in U.S.Pat. No. 4,553,614, whereby a spacer is provided and can be insertedbetween the facing ends of the pipe sections to be joined. The spacersconsists of segments that can be joined to form a ring between the endfaces of the pipe sections be joined. Such a pipe joint makes itpossible to adjust the mutual spacing of the pipe sections to be joinedwithout detaching the mutual screw connection of the pipe sections. Sucha spacing adjustment makes it possible, for example, to vary thepre-tension of an axial spring arranged between the shoulders of thepipe sections that are to be connected, but it is also associated withchanges in the rotatory alignment of the pipe sections to be joined.

SUMMARY OF THE INVENTION

The present invention discloses an especially simple design of anadjustable angle pipe joint that assures a closed transition between thepipe sections joined and offers various possibilities for mutualarrangement of the joined pipe sections.

The pipe joint according to the present invention consists of a fewsimple parts which permit both rapid and simple changes in arrangement.The pipe joint disclosed herein provides great joint strength so thatthe drill string casing is not weakened in the area of the pipe joint incomparison with a conventional thread joint. The pipe joint alsorequires only minor structural variations to implement differentpossible angle and part arrangements.

More particularly, the present invention discloses a universal,adjustable pipe joint which permits a wide variety of possibleadjustments with simple means in well drilling technology. In principle,the joint disclosed in this invention can be readily used for joiningarticles of all types which include tubular, pipe-like, projections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cutaway longitudinal section through an area of a drillstring casing to illustrate one embodiment of a pipe joint according tothe present invention;

FIG. 2 shows a cutaway longitudinal section through an area of a drillstring casing to illustrate another embodiment of a pipe joint accordingto the present invention;

FIG. 3 shows a cutaway longitudinal section through an area of a drillstring casing to illustrate yet another embodiment of a pipe jointaccording to the present invention;

FIG. 4 shows a cutaway longitudinal section through an area of a drillstring casing to illustrate a further embodiment of a pipe jointaccording to the present invention;

FIG. 5 shows a cutaway longitudinal section through an area of a drillstring casing to illustrate still another embodiment of a pipe jointaccording to the present invention;

FIG. 6 shows a cutaway longitudinal section through an area of a drillstring casing to illustrate yet a further embodiment of a pipe jointaccording to the present invention;

FIG. 7 shows a pipe joint according to the present invention whichincludes a stabilizer;

FIG. 8 shows a pipe joint according to the present invention whichincludes an eccentric stabilizer;

FIG. 9 shows a pipe joint according to the present invention whichincludes a wear protection sleeve;

FIG. 10 shows a pipe joint according to the present invention whichincludes an eccentric wear protection sleeve.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in greater detail and withspecific reference to the accompanying drawings. With reference now toFIG. 1, one embodiment of the present invention is shown.

FIG. 1 shows a cutaway diagram illustrating a first pipe section 1including an inside thread 2 on the end facing a second pipe section 3.The latter is also provided with an inside thread 4 on the end facingthe first pipe section 1.

These two pipe sections 1 and 3 that are to be joined are generally partof a drill string casing 5 and within it they may form the parts of anouter casing for a tool, e.g., for a motor for directional drilling, orpart of the drill string pipe itself. However, pipe sections I and 3 mayalso be part of a separate pipe joining device and may be provided witha connecting thread of a suitable type and design on the ends facingaway from the inside threads 2 and 4. In general, this is also true ofthe other embodiments illustrated in FIGS. 2-10.

The pipe joint in FIG. 1 includes a tubular inside part 6 which isprovided with outside threads 7 and 8 on each of its two ends. The twoinside threads 2 and 4 of the two pipe sections 1 and 3 are screwed tothe outside threads 7 and 8. The inside threads 2 and 4 of the pipesections 1 and 3 are designed as cylindrical threads and have a lengthgreater than the length required for an engagement that will assure asecure joint. This is also true of outside threads 7 and 8, likewisecylindrical, of the inside part 6. Accordingly, threads 2 and 7 and 4and 8, respectively, form adjusting thread pairs whose depth ofengagement is variable and which run in the same direction of rotation.

The pipe joining arrangement also includes a tubular outside part 9which can move over inside part 6 but which is non twistably supportedon inside part 6. For example, the axially moveable support, which isalso twistproof, can be implemented by a multispline profile, by splines10 that fit into grooves 11, or by some other suitable guidance andsecuring devices.

Outside part 9 includes end faces 12 and 13 which are in compressiveengagement with end faces 14 and 15, respectively, on the connectingends of pipe sections 1 and 3 when these sections are in thejoining/locking position. In the design shown in FIG. 1, all of the endfaces 12, 13, 14, and 15 are flat annular faces arranged in a planerunning at right angles to the longitudinal middle axis 16 of the insidepart 6. Furthermore, annular faces 12 and 13 of the outside part 9 haveinside and outside diameters that essentially correspond to the insideand outside diameters of annular faces 14 and 15 on the pipe sectionsthat are to be joined so that the respective end faces 12 and 14 and 13and 15 are essentially flush with each other and are in mutualcompressive engagement over their entire areas when the pipe sectionsare joined.

If the pitch of the threads in the thread pairs 2 and 7 and 4 and 8 isidentical, as shown in FIG.1, the inside part 6 can be axially adjustedrelative to the first or second pipe section 1 or 3 as illustrated bythe position of inside part 6 as shown with a dotted line. Thisadjustment makes it possible, for example, to alter the axial bias of anaxial spring package that is supported on one of the end faces of theinside part 6 or on an abutment supported by the inside part 6 on oneend and on the other end being supported on an abutment face belongingto the first or second pipe section 1 or 3. Furthermore, the axialadjustment of the inside part 6 relative to the pipe sections 1 and 3can also be used to vary the rotatory alignment of the inside part 6relative to the pipe sections 1 and 3, e.g., in order to vary the biasof a torsion spring held between the inside part 6 and one of the pipesections 1 or 3.

In all settings, the drill casing 5 can have a smooth continuous outsidecontour in the area of the joint of pipe sections 1 and 3, and, in thecase of a flush alignment of pipe sections 1 and 3, the drill casing 5also has a cylindrical outer contour when, as shown here, the outsidediameter of outside part 9 corresponds to the outside diameter of pipesections 1 and 3.

Furthermore, and as shown in FIGS. 7 and 8, since rotatory adjustment ofthe inside part 6 relative to pipe sections 1 and 3 is also associatedwith a rotatory adjustment of the alignment of outside part 9 relativeto pipe sections 1 and 3, the pipe joint according to this inventionalso makes it possible, for example, to use the outside part 9 as a toolor as a carrier for a tool, e.g., a stabilizer 50 or an eccentricstabilizer 60 that can be easily exchanged for a different stabilizerwith a different diameter and/or a different eccentricity. As indicatedin FIGS. 9 and 10, the outside part 9 could also comprise such tools asa wear-protection sleeve 70 or an eccentric wear-protection sleeve 80.Other tools could also include a ribbed stabilizer or an eccentric andribbed stabilizer; etc.; all of which could have an enlarged outsidediameter with respect to the outside diameters of the two pipe sections,1 and 3, to be joined. The specific nature and design of such tools iswell known in the art and the alignment of such a tool could be variedby the adjustment of outside part 9 relative to pipe sections 1 and 3.Of course, any such tools could be used with any of the pipe jointembodiments discussed herein and shown in the accompanying FIGS. 1-6.

To make an adjustment in the embodiment shown in FIG. 1, the engagementbetween either section 1 and part 9 or section 3 and part 9 is releasedwith the help of torque generators acting on the outside part 9 and onthe respective pipe section 1 or 3. Then the desired rotatory or axialadjustment of inside part 6 together with outside part 9 relative topipe section 1 or 3 is performed. Furthermore, while maintaining thealignment of either section 1 and part 6 or section 3 and part 6relative to each other, the joint position of the sections is restoredby rescrewing pipe section 1 or 3, in comparison with which a change inalignment of inside and outside parts 6 and 9 is of no relevance.

When outside part 9, for whatever reason, has such a small axialdimension that a torque-producing tool cannot be attached to it, the endfaces of a pair, 12 and 14 or 13 and 15, of end faces may either have anincreased coefficient of friction or may be provided with grooves orteeth, e.g., as illustrated in FIG. 6, in order to permit the desiredengagement or disengagement of the other pair of end faces. Foradjustment purposes in such a case, all that is necessary is to releasea coupling located near the facing teeth, for example between outsidepart 9 and one of the pipe sections 1 or 3, in order to be able toadjust the inside part 6 relative to the outside part 9 and thusrelative to the other pipe section.

The various pipe joint embodiments as discussed elsewhere herein couldalso be made with thread connection pairs 2 and 7 and 4 and 8 running inopposite directions of rotation. This arrangement could be used in caseswhere a safe connection is to be made up between two connecting pipesections 1 and 3 without the necessity of rotating either section 1 or 3once both outside threads 7 and 8 of inside part 6 are engaged with theinside threads 2 and 4 of the two pipe sections 1 and 3, respectively.The connection between pipes section 1 and 3 could then be easilytightened by only rotating outside part 9 and inside part 6 while pipesections 1 and 3 are held generally non-rotatable.

A second embodiment, as shown in FIG. 2, of a pipe joint according tothis invention corresponds to that embodiment shown in FIG. 1 anddiscussed hereinabove with the difference that the respective pitches ofthe pairs of threads 102 and 107 and 104 and 108, threads 102 and 104being the inside threads of pipe sections 1 and 3 respectively andthreads 107 and 108 being the outside threads of inside part 6, differfrom each other. In addition to the adjustment options of the versionaccording to FIG. 1, the embodiment shown in FIG. 2 also provides forthe possibility of varying the rotatory alignment of pipe section 1relative to pipe section 3 by axially adjusting the inside part 6relative to pipe sections 1 and 3. In this way, for example, the bias ofa torsion spring supported between pipe sections 1 and 3 can be variedor the alignment of an eccentric stabilizer arranged on one the two pipesections 1 or 3 may be changed.

In both versions, as shown in FIGS. 1 and 2, inside threads 2 and 4 and102 and 104 of pipe sections 1 and 3 respectively, have thread axes thatcoincide with the longitudinal middle axis of their respective pipesection 1 or 3. Likewise, the thread axes of outside threads 7 and 8 and107 and 108 coincide with the longitudinal middle axis 16 of inside part6 and thus also with the longitudinal middle axes of pipe sections 1 and3. It becomes clear that the pipe joint shown in FIGS. 1 and 2 offers nopossibility of forming a variable angle of bend between the pipesections 1 and 3. However, this possibility does exist in theembodiments shown in FIGS. 3-6 which will be discussed in greater detailhereinbelow.

The embodiment shown in FIG. 3 differs from those shown in FIGS. 1 and 2in that the inside thread of one of the pipe sections 1 or 3, the insidethread 202 of pipe section 1 in the example shown here, has a threadaxis 17 which, together with the longitudinal middle axis 18 of its pipesection 1, forms an acute angle 19. Such a pipe joint creates a tubebody known, for example, as a "bent sub" as used for directionaldrilling work. Nevertheless, all of the adjustments discussed withregard to the embodiments shown in FIGS. 1 and 2 are also possible inthe embodiment shown in FIG. 3. The possibility of a rotation adjustmentof pipe section 1 relative to pipe section 3 is especially important incases where pipe section 3 includes a bend and an alignment of the bendbetween pipe section 1 and pipe section 3 relative to the bend of pipesection 3 is desired.

It should also be pointed out that the end face 114 of pipe section 1,as shown in FIG. 3, is in a plane which, together with the longitudinalmiddle axis 18 of pipe section 1, forms an angle 20 that differs from90° and the amount of that angle's deviation from 90° corresponds to thesize of angle 19. This assures that end faces 12 and 114 are alignedparallel to each other and at right angles to thread axis 17 and that aclosed outer contour is preserved even in the area of the bend.

The embodiment shown in FIG. 4 differs from those shown in FIGS. 1 and 2in that an outside thread of inside part 6, outside thread 207 in theexample shown here, has a thread axis 21 which, together with thelongitudinal middle axis 16 of inside part 6, forms an angle 22. Thisversion offers similar possibilities for adjustment as those obtainedwith the version shown in FIG. 3, but in a pipe joint for pipe sections1 and 3 which includes coaxial thread axes of the two inside threads 2and 4 relative to the longitudinal middle axes of their respective pipesections 1 and 3.

Another difference between the embodiment shown in FIG. 4 and thoseshown in FIGS. 1 and 2 is that the end face 112 of outside part 9 is ina plane which forms an angle 23 with the longitudinal middle axis 16 ofinside part 6 where said angle differs from 90° by an amountcorresponding to size of angle 22. Thus, this version also incorporatesthe closed outside contour in the area of the bend because end faces 14and 112 are aligned so that they are parallel to each other.

In addition to the possible adjustments obtained with the embodimentshown in FIG. 3, there is also a possibility of varying the angle ofbend between pipe sections 1 and 3 in the embodiment shown in FIG. 4 byreplacing inside part 6 and outside part 9 with similar parts whoseangles 22 and 23 differ from those shown in the present example.

The embodiment shown in FIG. 5 differs from those shown in FIGS. 1 and 2in that the middle axis of the inside thread of a pipe section 1 or 3,thread axis 24 of inside thread 302 of pipe section 1 in the exampleshown here, forms an acute angle 26 with the longitudinal middle axis25. This is similar in form to the embodiment shown in FIG. 3. As shownin FIG. 5, the alignment of the end face 114 is at right angles to thelongitudinal middle axis 24 of inside thread 203.

Another difference is that the thread axis 27 of outside thread 307 ofinside part 6, which coincides with thread axis 24 in FIG. 5, forms anacute angle 28 with the longitudinal middle axis 16 of inside part 6 andthe size of this angle may correspond to or differ from the size of theangle 26. End face 212 on outside part 9 runs in a plane which, togetherwith the longitudinal middle axis 16 of inside part 6, forms an angle 29that differs from 90° and the size of that angle's deviation from 90°corresponds to the size of angle 28. Thus, a closed outside contour inthe area of the bend is also assured in this version by the parallelarrangement of end faces 114 and 212.

In the embodiment shown in FIG. 5, a continuously adjustable angle ofbend can be formed between pipe sections 1 and 3 and the possibleadjustments cover an angle range whose upper limit value is defined bythe sum of angles 26 and 28 and it lower limit is defined by thedifference between angles 26 and 28. This range includes an angle ofbend of 0° in the case when angles 26 and 28 are equal in size. Such acontinuous adjustment of the angle of bend is independent of particularspacing measures and is also free of variations in distance between pipesections 1 and 3.

The embodiment shown in FIG. 6 differs from those shown in FIGS. 1 and 2in that the thread axis 30 of inside thread 302 of pipe section 1 formsan acute angle 33 with its longitudinal middle axis 31, thread axis 34of outside thread 307, which coincides with thread axis 30, forms anacute angle 35 with the longitudinal middle axis 16 of inside part 6,thread axis 36 of outside thread 308 of inside thread part 6 forms anacute angle 37 with its longitudinal middle axis 16, and thread axis 38of pipe section 3, which coincides with thread axis 36, forms an acuteangle 40 with its longitudinal middle axis 39. End faces 312 and 314 areparallel to each other and aligned at right angles to the longitudinalmiddle axes 34 and 30, and end faces 313 and 315 of part 6 and section3, which form part of the facing teeth, run in planes parallel to eachother and forming an angle of 90° with the longitudinal middle axes 36and 38

Such a design makes it possible to achieve a variable axial offsetbetween the longitudinal middle axes 31 and 39 of pipe sections 1 and 3with identical angles 33, 35, 37, and 40. An angle of bend between pipesections 1 and 3 can also be implemented where the maximum valuecorresponds to the sum of the angles 33, 35, 37, and 40. In this way, arelatively great total angle of bend ca be achieved with relativelysmall bends in the thread axes.

Furthermore, there is also the possibility of creating a variable doublebend piece with different sizes of angles. For example, angles 33 and 35are made identical to each other and angles 37 and 40 are also madeidentical to each other so that the resulting angle of bend is betweenthe first pipe section 1 and the second pipe section 3, but at the sametime the intermediate range between the ends of pipe sections 1 and 3formed by outside part 9 has an opposite bend. Such a design isespecially important for and useful in navigational drilling tools.

In the foregoing specification, this invention has been described withreference to specific exemplary embodiments thereof. It will, however,be evident that various modifications and changes may be made thereuntowithout departing from the broader spirit and scope of the invention asset forth in the appended claims. The specification and drawingsincluded herein are, accordingly, to be regarded in an illustrativerather than in a restrictive sense.

What is claimed is:
 1. A pipe joint for a first and second pipe section,said pipe sections forming part of a drill string casing and includingopposing end faces and an inside thread on their facing ends, said pipejoint comprising a tubular inside part which has an outside thread oneach of its opposite ends wherein the outside threads run in the samedirection of rotation, one of said ends being screwed to the insidethread of the first pipe section and the other of said ends beingscrewed to the inside thread of the second pipe section, and a tubularoutside part comprising a tool and including opposite end faces that canmove axially over said inside part, and which is non-twistably supportedon said inside part, so that when the pipe sections are in a joinedposition, the opposing end faces of the pipe sections are in acompressive engagement with the opposite end faces of the outside part.2. A pipe joint according to claim 1, wherein said tool comprises astabilizer.
 3. A pipe joint according to claim 1, wherein said toolcomprises an eccentric stabilizer.
 4. A pipe joint according to claim 1,wherein said tool comprises a wear protection sleeve.
 5. A pipe jointaccording to claim 1, wherein said tool comprises an eccentric wearprotection sleeve.
 6. A pipe joint for a first and second pipe section,said pipe sections forming part of a drill string casing and includingopposing end faces and an inside thread on their facing ends, said pipejoint comprising a tubular inside part which has an outside thread oneach of its opposite ends wherein the outside threads run in oppositedirections of rotation, one of said ends being screwed to the insidethread of the first pipe section and the other of said ends beingscrewed to the inside thread of the second pipe section, and a tubularoutside part including opposite end faces that can move axially oversaid inside part and which is non-twistably supported on said insidepart, so that when the pipe sections are in a joined position, theopposing end faces of the pipe sections are in a compressive engagementwith the opposite end faces of the outside part.
 7. A pipe jointaccording to claim 6, wherein the outside part comprises a tool.
 8. Apipe joint according to claim 7, wherein said tool comprises astabilizer.
 9. A pipe joint according to claim 7, wherein said toolcomprises an eccentric stabilizer.
 10. A pipe joint according to claim7, wherein said tool comprises a wear protection sleeve.
 11. A pipejoint according claim 7, wherein said tool comprises an eccentric wearprotection sleeve.
 12. A method for forming a pipe joint for a first andsecond pipe section, said pipe sections forming part of a drill stringcasing and including opposing end faces and an inside thread on theirfacing ends, said pipe joint comprising a tubular inside part which hasan outside thread on each of its opposite ends wherein the outsidethreads run in the same direction of rotation, and a tubular outsidepart including opposite end faces that can move axially over said insidepart and which is non-twistably supported on said inside part, saidmethod comprising the steps of:screwing one end of the inside part intothe first pipe section; screwing the other end of the inside part intothe second pipe section thereby forming a loose pipe joint; and rotatingthe inside part and one of the first or second pipe sections while theother of the first or second pipe sections is held generallynon-rotatable thereby tightening said pipe joint and bringing theopposing end faces of the first and second pipe sections into acompressive engagement with the opposite end faces of the outside part.13. The method of claim 12 further including the step of adjusting theinside part with respect to one of the first or second pipe sectionswhile tightening the pipe joint.
 14. The method of claim 12 furtherincluding the step of adjusting the inside part with respect to both ofthe first and second pipe sections while tightening the pipe joint. 15.The method of claim 12 further including the step of aligning theoutside part with respect to one of the first or second pipe sectionswhile tightening the pipe joint.
 16. The method of claim 12 furtherincluding the step of aligning the outside part with respect to both ofthe first and second pipe sections while tightening the pipe joint. 17.A method for forming a pipe joint for a first and second pipe section,said pipe sections forming part of a drill string casing and includingopposing end faces and an inside thread on their facing ends, said pipejoint comprising a tubular inside part which has an outside thread oneach of its opposite ends wherein the outside threads run in oppositedirections of rotation, and a tubular outside part including oppositeend faces that can move axially over said inside part and which isnon-twistably supported on said inside part, said method comprising thestep of:screwing one end of the inside part into the first pipe section;screwing the other end of the inside part into the second pipe sectionthereby forming a loose pipe joint; and rotating the inside part whilethe first and second pipe sections are held generally non-rotatablethereby tightening said pipe point and bringing the opposing end facesof the first and second pipe sections into a compressive engagement withthe opposite end faces of the outside part.
 18. The method of claim 17further including the step of adjusting the inside part with respect toone of the first or second pipe sections while tightening the pipejoint.
 19. The method of claim 17 further including the step ofadjusting the inside part with respect to both of the first and secondpipe sections while tightening the pipe joint.
 20. The method of claim17 further including the step of aligning the outside part with respectto one of the first or second pipe sections while tightening the pipejoint.
 21. The method of claim 17 further including the step of aligningthe outside part with respect to both of the first and second pipesections while tightening the pipe joint.